It is required that this specification comply with paragraph 1.71 (b) of 37 CFR 1.1 Therefore, to distinguish the solicited patent from the present methods of instant photography, which for many applications the solicited would supplant, this will review the technical shortcomings and limited number of end applications of present methods; and the superior advantages of the solicited patent will be described.
No doubt, first thought to obtain an instant picture displayed on a cathode-ray tube is to simply focus an instant camera on the screen, but the effort for suitable results is not that simple and the result is a limited-size opaque print. Moreover, there are serious technical factors of this method which necessarily degrade the quality of any opaque picture of the displayed image. These factors are:
1. An imprecise mechanical camera shutter mechanism to "freeze" a single cathode-ray tube frame in 1/30th of a second.
2. Ambient visible light reflected by the cathode-ray tube faceplate, unless picture is taken in total darkness.
3. Halation effects between the outer and inner surfaces of the faceplate.
4. Loss of contrast ratio due to faceplate curvature.
5. Limited resolution imposed by the internal color mask.
6. Limited resolution imposed by the discrete color phosphor structure.
7. Non-linearities of vertical and horizontal sweeps.
8. Aberration of the electron beam(s).
9. The number of scanning lines per raster, depending upon sweep standard.
10. Different aspect ratios of cathode-ray tube and film.
11. Adjustment of monitor image quality by judgment of operator. (Color of this invention is in film; it is not generated by phosphor.)
Aside from the technical shortcomings inherent in the use of a Polaroid or Eastman-type instant camera to capture a cathode-ray tube image, there are desirable commercial and popular uses of pictures which those cameras do not address:
1. Instant color pictures as opaque prints are unuseable in slide projectors.
2. No instant camera of any size yields an instant color transparency for optical projection.
3. No instant camera yields black-and-white color separations of an image for use in the graphic arts industry.
The proposed process of this invention captures an instant color slide of a displayed cathode-ray tube image, not as the Polaroid/Eastman method, but by means of the video signals on the control grids of the display monitor. Simply, a "slave" ultraviolet-emitting cathode-ray tube to the monitor is used to print onto what are known in the graphic arts industry as diazo films.
Appropriate as a "slave" tube is a small, projection-type cathode-ray tube, one with a fine, continuous-phosphor ultraviolet-emitting screen on the inner surface of a fiber-optic, optically-flat, 35 mm size faceplate. Exposure of each diazo color film for a full-color transparency slide, or black-developing diazo for a separation of each color, is preferred by direct contact with the faceplate. Thus, the preferred miniature "slave" or printer cathode-ray tube would "paint" an ultraviolet image through its fiber-optic faceplate onto the diazo film, an image not degraded by the faults inherent in the Polaroid/Eastman method. And because the process of this invention utilizes ultraviolet light for exposure of the diazo films, these can be developed in ambient light. The process therefore is a "daylight" one, not requiring the use of a photographic darkroom.
Since the slow-printing, diazo films must be exposed to a still utraviolet image on the face of the printer cathode-ray tube, it is necessary, if the monitor cathode-ray tube were to display a moving picture, that there be a means to repetitively display a single frame. Therefore the preferred system would operate to enable frame storage and playback by devices known as "frame grabbers" or having the capability of "frame freezing." The playback of the "frame grabber" then would be into the printer as well as the monitor cathode-ray tube.
Following are principal reasons the use of the preferred "slave" cathode-ray tube would yield pictures superior to those obtainable either by means of instant or conventional photography of a cathode-ray tube image:
1. A small "slave" cathode-ray tube would preclude nonlinearities of vertical and horizontal deflections.
2. Electron-beam size would remain constant with its short trajectory; the ultraviolet image therefore would be "painted" uniformly.
3. The uniform powder deposit of the ultraviolet-emitting phosphor on the inner surface of the "slave" faceplate, unlike the discrete triad phosphor pattern of the monitor cathode-ray tube, would be activated on each horizontal sweep by all video frequencies.
4. With an assumed 35 mm fiber-optic faceplate of even 20 micron fibers (plates of 7 micron fibers are manufactured), resolution of an exposed diazo image would be limited only by the resolution of the television system. With 7 micron fibers, a derived color separation would be practically continuous tone.
To teach the solicited patent "in such full, clear, concise, and exact terms as to enable any person skilled in the art or science to which the invention or discovery appertains (para. 1.71 (a), 37 CFR) . . . to make and use the same," this specification will continue with descriptions, first, of the important component elements of the printer cathode-ray tube, including its electron-gun, the preferred ultraviolet-emitting phosphor, and its fiber-optic faceplate. This will be followed by a description of the preferred film to be used for the inventive concept. Thereafter, objects of the invention will be set forth and followed by reference to drawings of a number of preferred slide recorder systems which embody the invention. This order of presentation is adopted so that a full understanding of the invention's key elements is gained in anticipation of their combination in the preferred systems.
Within the printer cathode-ray tube it is the electron gun which "paints" the video signal on the faceplate phosphor. And the intensity of ultraviolet emitted by the preferred phosphor is proportional to the beam density "projected" by the gun. Therefore, inasmuch as it is desirable that the preferred systems of this invention operate to expose the preferred film in as short a time possible, the use of an electron gun with the highest possible beam density, without loss of focus, is preferred. One such electron gun is said to be the Laminar-flo electron gun advertised by Watkins-Johnson, Palo Alto, CA. 94304. The use of the gun, or equivalent, in the printer cathode-ray tube, no doubt, would enhance phosphor ultraviolet emission.
The electron beam of the printer cathode-ray tube, as said, "paints" an image on an ultraviolet-emitting phosphor. Therefore, it is appropriate here to review a characteristic of the ultraviolet spectrum and phosphors which emit within that spectrum and their applicability to the inventive concept.
The invisible spectrum of ultraviolet is considered from 4000 to 1600 Angstrom units, and many phosphors emit ultraviolet within this region. One, P47 phosphor, for example, has an emission curve that peaks at approximately 4000 Angstrom units. Applicability of it and others to the invention, although theoretically sound, is inappropriate and practically inoperative, however, because of their low luminescent radiant efficiency. The low efficiency of conversion of electron beam power into ultraviolet emission is intolerable because it results in inordinately long times to properly expose the preferred film. This was the known phosphor "state of the art" with respect to ultraviolet emission up to the end of 1975, when announcement of a "breakthrough" phosphor, not as applicable to this inventive concept, but for X-ray screens, was published in a scientific journal.
First known mention of the "breakthrough" phosphor is believed to be in Philips Research Laboratories' publication, Medica Mundi, Vol. 20, No. 12, 1975, in a paper entitled, "New phosphors for X-ray screens," by Dr. A. L. N. Stevels. As can be readily interpreted from the paper, phosphor BaFCl:Eu.sup.2+, the ultraviolet-emitting "breakthrough," was developed for use in X-ray screens: its substantially higher luminescent radiant efficiency under X-ray excitation would make for significantly lower X-ray doseages of patients. Dr. Stevels' paper in Medica Mundi was followed by another of his in the Journal of the Electrochemical Society, June 1976, with A. D. M. Schrama-de Pauw, paper entitled, "Theoretical and Experimental Efficiencies of X-ray Screens."
Both papers reveal the significant characteristics of phosphor BaFCl:Eu.sup.2+, applicable not only for X-ray screens, but for use in the "slave" cathode-ray tube of the present invention. Other phosphors mentioned in both papers and considered to be significant to this invention are: BaFBr:Eu.sup.2+, also a powder phosphor; and CsI:Na, a vapor-deposited phosphor. For this invention, however, and inasmuch as it has been in production for X-ray screens by GTE Sylvania since the Spring of 1977, phosphor BaFCl:Eu.sup.2+ is immediately pertinent. Phosphor BaFBr:Eu.sup.2+ is considered applicable despite the "afterglow" property mentioned in the Medica Mundi paper. (The afterglow is less significant than the higher luminescent radiant efficiency, since the invention is concerned with the printing of individual still images, not of a succession of frames for a moving one.)
It is appropriate to state here that Dr. A. L. N. Stevels is the son of Dr. Johannes Marinus Stevels, until recent years Chief Chemist of Philips Research Labs., Eindhoven, Netherlands.
The significant characteristics of phosphor BaFCl:Eu.sup.2+ with respect to this invention are illustrated in FIG. 6:
1. Its emission spectrum includes the greater range of the diazo sensitivity curve (No. 5);
2. Its luminescent radiant efficiency is more than double that of P47 (No. 1), which prior to Dr. Stevels' papers was regarded by tube manufacturers in this country as the "state of the art" for ultraviolet emission.
3. The stated luminescent radiant efficiencies are measured under 20 KV cathode-ray tube excitation.
It is considered that phosphor No. 2, tentatively recommended by another phosphor chemist of Philips Laboratories may also be applicable, though its production status is unknown. The same is true of phosphor No 4.
Here, it is now pertinent to state that the phosphor screen of the printer tube may be aluminized so that the ultraviolet light emitted by the phosphor through the fiber-optic faceplate is approximately doubled due to the reflected light of the aluminum coating. Whether or not the printer need be aluminized may well depend upon factors of image resolution and practical times of film exposure required by a particular preferred system of which the tube is a part.
It is impractical to practice this invention by the contact exposure of a diazo film against the surface of a conventional cathode-ray tube faceplate: With such a faceplate, each point of light emitted on the inner surface would disperse in all directions through the thickness of the plate, striking and exposing many points of the film--with a resulting diffuse, unsharp film image. Therefore it is appropriate to describe the preferred type of fiber-optic faceplate to practice this invention--one which will "paint" a sharp, useable image on the diazo film exposed in contact with it.
The preferred fiber-optic faceplate for the printer tube is one manufactured by such companies as Galileo Electro-Optics Corp., Sturbridge, MA., 01518; also, Canon, U.S.A., Inc., Lake Success, N.Y., 11040, and other companies. Cathode-ray tube manufacturers which produce tubes with fiber-optic faceplates include, Westinghouse Electric, Westinghouse Circle, Horseheads, N.Y., 14845; DuMont Electron Tubes, Clifton, N.J., 07015; also, Thomas Electronics, Inc., Wayne, N.J. 07470.
Of its fiber-optic plates, Galileo states in a data sheet, ". . . the basic function of the fiber-optic faceplate is to transfer an image into or out of a vacuum enclosure." Also, "Faceplates with high-numerical aperture and good near ultraviolet transmission characteristics are useful with ultraviolet-emitting phosphors." Galileo manufactures fiber-optic faceplates with nominal fiber diameter of 7 microns, and palte size 3-inches wide by 3-inches long by 0.2-inches thick, larger than the preferrerd 35 mm size. In a cathode-ray tube, these plates withstand an accelerating voltage as high as 20 KV, which voltage, it should be observed, is that at which the luminescent radiant efficiency of the preferred ultraviolet-emitting phosphor is meaured.
Before a discussion of the characteristics of the preferred diazo films, it is in order to review briefly the two basic systems of color. Pertaining to visible light are the three primary additive colors red, green and blue. As seen on color television, when these three light primaries in appropriate proportions are combined by the eye, a sensation of white is observed. If the three primaries are added disproportionately, the white becomes tinted by the color of the predominant primary light. This additive system applied to light; it does not apply, for example, in the graphic arts to the magazine printing of color pictures, or in photography, to the processing (darkroom or instant) of opaque color prints. These involve the subtractive system of color with printing inks or dyes of colors magenta, cyan and yellow. How, then, is a color slide reproduction produced by the printer of the preferred systems with the use of films which develop the subtractive colors, when the color image on the monitor tube is observed by reason of emitted additive colors?
In explanation, the following paragraphs will describe how a red area of a scene viewed on a monitor cathode-ray tube is reproduced on a diazo film slide.
In the printer cathode-ray tube, "slave" to the monitor, the additive primary red video signal "paints" an ultraviolet image, and it is this image created by the preferred phosphor that is projected through the fiber-optic faceplate onto the diazo film. In this instance, the film in contact with the plate is one which develops the subtractive primary color cyan (bluish green). As a result, the exposed area of the film becomes desensitized, and upon development of the film in ammonia vapors the area remains transparent. The unexposed area of the film, however, turns the color cyan during development. (It should be realized that when one views a printed picture, one sees a color after incident white light has been reflected by the white paper through the printed subtractive inks or dyes.) When white light therefore is directed on the cyan film, one sees only cyan because red light has been absorbed by the film coating. When all three subtractive primary films are superimposed, it follows that the area of the cyan film exposed to ultraviolet representative of the red signal will be transparent, but the overlap of the corresponding areas of the magenta and yellow films will produce red--in the same area as shown on the monitor cathode-ray tube.
The full-color slide is produced by the development and superposition of the following three subtractive films: (1) The film which develops cyan when exposed to the ultraviolet image of the red signal; (2) The film which develops magenta after exposure to the ultraviolet image of the green signal; (3) The film which develops yellow after exposure to the ultraviolet image of the blue signal.
Thus, in the illustration above, the areas on the second and third films which correspond to the red signal area of the first film will be magenta and yellow, respectively. It remains to state that the magenta film will absorb green light from white light, and the yellow film will absorb blue light from white. The remaining unabsorbed spectrum will be red--corresponding to the original red area. By a similar analysis all visible colors of the spectrum can be reproduced by the films.
Now to consider the ultraviolet-sensitive films preferred for this invention; they are known as diazo films, and have maximum sensitivity in the ultraviolet spectrum between 3600 and 4000 Angstrom units. They develop the three subtractive primary colors magenta, cyan and yellow and black, and a number of other colors, by exposure to ammonia vapors.
The films have been in common use in the graphic arts industry for over 25 years, generally to color proof separations produced by conventional photographic methods. For that useage, the low sensitivity of the films to ultraviolet light is tolerable because the films are exposed through the photographic separations either by means of high-intensity arc lamps or mercury-vapor lamps, both rich in ultraviolet. In that useage the low sensitivity of the films is offset by the high ultraviolet emission of the lamps.
In this invention a short exposure time of the diazo films requires the highest possible phosphor emission of ultraviolet through the faceplate of the printer cathode-ray tube. It will be realized at this point that the diazo films have never been used, nor can they be, in a conventional camera with film exposures in fractions of a second. The preferred diazo films, and others applicable to the inventive concept, require exposure times in the order of seconds. It is appropriate here to cite first the manufacturers of the preferred ammonia-developing diazo films; they include the Ozalid Division of GAF; Tecnifax, a division of Scott Paper Company; Keuffel & Esser Company, and others. It is probable, too, that the preferred films are manufactured worldwide, whereas other applicable films are not because of their proprietary nature.
Other films applicable to the inventive concept, by reason of their sensitivity to the ultraviolet spectrum, are the Color Key films of the 3-M Company. These films have been on the market for approximately 15 years and are developed by solution. They are available in the process colors cyan, magenta, yellow and black.
The third color-proofing system available to the graphic arts industry, and applicable as well to the inventive concept, is the "Chromalin" system of the Du Pont Company. The system of ultraviolet-sensitive films was introduced in 1972 and makes use of dry toners or powders of the subtractive primary colors, as well as a range of other colors, to develop the color of each separation.
Still another available ultraviolet-sensitive film applicable to the inventive concept, not for the production of color slides, but for black-and-white color separations is the heat-developing film Kalvar, marketed by Canon, U.S.A., as the Canon/Kalvar System.
Having described the basic inventive concept, the several means to implement the concept and pertinent color theory, the applicant here respectfully sets forth the objects of his invention.